Japan has dismissed pressure from US lawmakers to issue a fresh apology over its use of sex slaves, known as comfort women, during World War II.

A US Congressional committee passed a resolution on Tuesday calling for further apologies over the coercion of women into wartime brothels.

But the Japanese government said it did not want to add to its previous statements on the issue.

It also stressed that its alliance with the US was "unshakeable".

Japan says it has shown sufficient remorse over the issue, but survivors and relatives say it should go further.

Remorse

The House of Representatives' Committee on Foreign Affairs overwhelmingly approved the non-binding resolution.

The document urges Japan to "formally acknowledge, apologise and accept historical responsibility in a clear and unequivocal manner" for the coercion of young women into sexual slavery.

It also accuses Japanese officials of seeking to "dilute or rescind" a 1993 government statement which expressed its apologies and remorse for the suffering of comfort women, and acknowledged official involvement in the management of the brothels.

Historians estimate that around 200,000 women from across the Far East were forced to work as sex slaves in military brothels during World War II.

Prime Minister Shinzo Abe caused an uproar in March when he said there was no proof that the government or the military had forced the women into sexual servitude.